Department of Computer Science and Information Systems
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Item Linear phase FIR filter for narrow-band filtering(IEEE, 2008) Gudino, Lucy J.This paper proposes a novel approach to the design of linear phase, sharp transition, lowpass FIR filter. The filter has narrow transition band, low passband ripple and good stopband attenuation with reduced arithmetic complexity. The frequency response model of the filter is formulated using trigonometric functions of frequency to reduce the ripples due to Gibbpsilas phenomenon and to evaluate the impulse response coefficients in closed form. FIR highpass and bandpass filters of any passband width can also be designed using the proposed approach.Item A novel design of sharp transition FIR filter for digital beamforming(IEEE, 2008) Gudino, Lucy J.This paper proposes a new approach to the design of linear phase, equiripple response, lowpass FIR filter for digital beamforming applications. The simple filter design without optimizations has sharp transition, good stopband attenuation with less filter complexity. An uniform linear array beamformer with a narrow transition bandwidth and low side lobes is synthesized with fewer sensor elements. This is achieved by using the proposed filters as subfilters in the frequency response masking approach. Precise and independent specification of main beamwidth and side lobe level for the beamformer is possible.Item A new filter design for uniform linear array(IEEE, 2008) Gudino, Lucy J.In this paper, a new design of spatial filter for uniform linear array is presented. The array factor is expressed in terms of cosine, sine and linear functions of frequency which serves as an alternative to Chebyshev polynomials. The simple filter design has good stopband attenuation with the use of trigonometric functions with less filter complexity. Novel slope equalization technique of the filter design reduces ripples at the transition edges hence further improves its stopband attenuation. Proposed filter replaces Dolph-Chebyshev window in the design of a uniform linear array beamformer.Item A novel filter design for spatially interpolated beamformer(IEEE, 2009) Gudino, Lucy J.This paper proposes a novel design approach for a linear phase lowpass FIR filter for digital beamformer applications. The simple filter design has good stopband attenuation with the use of trigonometric functions and less filter complexity. Novel slope equalization technique of the filter design reduces ripple at the transition edges of the filter hence further improves its stop band attenuation. Proposed filter replaces Dolph-Chebyshev window in the design of a uniform linear array spatially interpolated beamformer. The resulting beamformer yields narrow main beamwidth and low sidelobe level with reduced complexity. The beamformer provides for precise and independent control of main beamwidth, null to null main beamwidth and sidelobe level.Item Expectation Maximization - Matrix Pencil Method for Direction of Arrival estimation(IEEE, 2010) Gudino, Lucy J.In this paper, we present a Direction of Arrival estimation algorithm by combining Expectation Maximization (EM) and Matrix Pencil Method (MPM). It is possible that, when using a long uniform array, a few elements may fail, or the half-wavelength spacing between the elements may not be satisfied due to the spatial constraint. Under such situation, the array is known as sublattice array, which is a NonUniform Linear Array (NULA). Well known Matrix Pencil Method (MPM) cannot be directly applied for sublattice array, because the MPM technique exploits the uniform array geometry. The proposed method is a combination of the EM and the MPM technique. The EM algorithm estimates the output of the omitted or missing elements to form an equivalent output of the uniform linear array, and then, the application of MPM is possible. This technique improves the performance significantly and also has the computational advantage, when the sublattice array is considered.Item Design of novel sharp transition multiband FIR filter(IEEE, 2010) Gudino, Lucy J.This paper presents the synthesis of a linear phase, sharp transition, multiband FIR filter. The frequency response model of the filter is formulated with equiripple passband, stopband regions using trigonometric functions and well defined linear transition region. Employing trigonometric functions reduces Gibb's phenomenon which is further reduced using variable density of ripple cycles in passband and stopband regions. Large density of ripples cycles are introduced at the transition edges which reduces the abrupt discontinuities at these edges. Thus passband ripple reduces and stopband attenuation improves. Slope equalization technique is applied to further reduce Gibb's phenomenon. Using the filter model, for the desired filter specifications, a closed form expression for impulse response coefficients is derived. The design allows for variation in center frequency, number and width of passbands, transition bandwidth, passband ripple and stopband attenuation without the need of separate design. The proposed design is simple, analytical, gives narrow transition bandwidth, less passband ripple, good stopband attenuation with less filter order.Item Synthesis of Adaptive Interpolated Beamformer(IEEE, 2010) Gudino, Lucy J.In this paper, synthesis of Adaptive Interpolated Beamformer (AIB) which is an adaptive version of Spatially Interpolated Beamformer is introduced. The AIB consists of a sparse beamformer whose weights are updated using Steepest Descent Constant Modulus Algorithm (SD-CMA). The spatial interpolation produces grating lobes which are eliminated using a spatial masking filter. Two forms of AIB are synthesized, one uses Chebyshev spatial masking filter and the other uses Type-I spatial masking filter. Update expression for weight vector of AIB is derived. AIB achieves superior adaptability and spatial discrimination with narrow beamwidth and produces deeper nulls in the direction of interferences with fewer physical antenna elements compared to conventional SD-CMA adaptive beamformer. Simulation studies demonstrate AIB using Type-I spatial masking filter offers better nulling of interferences because of its superior tapering sidelobe characteristics compared to Chebyshev masking filter. AIB is suitable in beamforming applications where very narrow beam is required employing less number of antenna elements.Item Development of adaptive beamforming algorithms for wireless communication networks(IEEE, 2011) Gudino, Lucy J.It is required to provide enough capacity in the wireless communication system due to increased number of users as well as new high bit rate services being introduced. One of the most promising techniques for increasing the capacity is smart antenna based space division multiplexing. One approach to implement smart antennas is based on array beamforming, where a narrow main beam is directed towards the desired user direction, while the nulls or the sidelobes with very low levels are adjusted towards other users. Recently, smart antennas have been proposed as a promising solution that can significantly increase the data rate and improve the quality of wireless transmission, which is limited by interference, local scattering, and multipath propagation. The antenna array is combined with digital signal processing to give a narrow beam pattern in response to the received signal by the smart antenna. The weights of the beamformer is calculated by using the adaptive approach which uses reference signal and the direction of the user based on the received signal. The main beam is then directed toward the specific user, while the nulls are adjusted toward the interferers.Item Implementation of multi-hop time synchronization on miniature test-bed setup of underwater acoustic sensor network(IEEE, 2014) Gudino, Lucy J.Time synchronization is an important part of any distributed networked embedded system. It is essentially the process of achieving and maintaining common time base among all network nodes of the system. This task is quite challenging for the systems or applications like sensor networks, since these systems are highly resource constrained, yet need to process time-sensitive data in collaborative manner. Though many protocols have been suggested for terrestrial sensor networks (RSB, TPSN, FTSP and LTS) and they perform reasonably well, very few protocols (THSL, Tri-message) have been suggested for the high-latency underwater acoustic networks, since achieving time-synchronization for high-latency networks is even more challenging issue. Here we describe a very simple extension and implementation of Tri-message time synchronization protocol for multi-hop Underwater Acoustic Sensor Network (UASN) on the miniature test-bed setup.Item Performance analysis of rectangular, triangular and E-shaped microstrip patch antenna arrays for wireless sensor networks(IEEE, 2014) Gudino, Lucy J.Generally wireless sensor nodes have been using omni-directional antennas to broadcast data. But these antennas are not very efficient as they suffer from poor spatial reuse, high collisions, decreased throughput and are not energy efficient. Usage of directional antennas which radiate in a particular direction is more efficient as it can lead to significant energy savings. They reduce beamwidth by concentrating power in a certain direction. In this paper, the performance of conventional omni-directional quarter wave monopole antenna, rectangular patch antenna array, triangular patch antenna array and E-shaped patch antenna array are compared. The antenna arrays have been designed, simulated and tested. The antenna arrays designed are fabricated and then are mounted on a sensor node. The performance analysis in terms of power consumption, received signal strength and packet delivery ratio is performed for individual antenna arrays